Ringing arrangement for electronic switching systems



Dec. 27,1949

RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS Filed Feb. 19, 1946 D. H. RANsoM 2,492,179

4 Sheets-Sheet 1 SUBSCWB.

SET

, INVENTOR. DAV/D H. RA/Vo/w Dec, 27, 1949 D. H. RANsQM 2,492,179

RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS L; v ATQRNEY Dec. 27, 1949 D. H. RANsoM 2,492,179

RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS Filed Feb. 19, 1946 4 Sheets-Sheet 4 PULSE SHAPING AMPMFlER 1N V EN TOR. QA V/D H. RH/VSUM /1 TTORNE'Y Patented ec. 27, 1949 RINGING ARRANGIEMEN` FOR ELECTRONIC l SWITCHING SYSTEMS David I-I. Ransom, Montclair, N. J., assignor to Federal Telecommunication Laboratories, Inc., New York, N. Y., a corporation of Delaware Application February 19, 1946, Serial No. 648,758

7 Claims.

This invention relates to new and useful improvements in communication systems and more particularly in telephone systems of the type disclosed in the copending application of E. M. Deloraine, Serial No. 628,613, filed Nov. 14, 1945.

The object of the present invention is to provide a ringing and an improved two-way talking arrangement for an all-electronic telephone exchange system, i. e. one in which no electromagnetic equipment is used for establishing connections.

With this object in view, I provide an elec-r tronic repeater through which two-way signaling may be accomplished, including the sending of a ringing signal from the central exchange to the called line.

In accordance with the embodiment here disclosed two electronic means such as cathode ray tubes are provided in common for the lines. Signals such as dial and speech signals may be sent from both the calling and the called lines through one of the cathode ray tubes, and signals such as speech and ringing signals may be sent to the line through the other cathode ray tube.

These and other features of the invention will more readily appear from the appended claims and the vfollowing detailed description of a prefer-red embodiment, of Vwhich as much as is necessary for an understanding of the invention is illustrated in Figs. 1 to 4 of the drawings. In reading the drawings, Fig. 2 should be placed below Fig. l, Fig. 4 to the right of Fig. 2 and Fig. 3 to the right of Fig. l, Figs. 1 and 3 being kept horizontal and Figs. 2 and 4 Vertical.

Fig. 1 shows the substation equipment of one line and the two electronic means and associated equipment common to the lines, the upper part oi' Fig. 2 the line iinder, and the lower part the talking circuit and signal repeater equipment, Fig. 4, the registering and line selecting equipment and Fig. 3 the dial pulse and ringing equipment.

Each subscribers line is provided with a subset I of any conventional type, a calling dial 2 by means of which, in the embodiment here disclosed, one to twenty impulses may be sent depending on the designation of the called line, a hybrid coil 3, and a balancing network 4. The interconnection of calling and called lines is effected by means of a pair of cathode ray tubes of which is employed for receiving signals (including speech) from the line and 6 for transmitting signals (including speech, ringing, and the like) tothe lines. The lines terminate on electrodes forming dynodes in the cathode ray tubes, one Winding of the hybrid coil 3 being connected to terminal electrodes of tube 5 and another winding to the electrode terminals of tube 6. Each tube is equipped with the custernary gun structure kand deecting means for the purpose of sweeping cyclically and in succession the line terminal electrodes provided therein. The beams of these tubes may, for instance, rotate (assuming that the line terminals are arranged in a circle) under the control of a master oscillator I operating at 200 kc. and connected in multiple with the deflecting plates of the two tubes through a. 1.0 kc. frequency divider 8 and a o phaser' 9, insuring a repetition rate of 10 kc. per second of the scanning beam.

4When the subscriber at station I initiates a call the operation of the switch hook (not shown) at the subset I places a negative potential on the anode I2 through the dynode of the calling line in the receiving tube 5 over a circuit extending from the negative pole of grounded battery I0 over a retardation coil Il, a loop including the secondary of the hybrid coil 3, the subset I, and dial 2. This causes a ow of electrons from the terminating electrode in the tube to anode I2 each time the scanning beam sweeps over the dynode of this line. The resulting negative pulse I3 is fed to the grid of a cathode follower and inverter tube I4. The negative pulses I5 in the cathode output of tube I4 are applied to the grid of a clipper amplifier tube I6. Tube I6 is normally biased by resister I'I to draw current, and the signal amplitude is so adjusted that each negative pulse I5 will drive the tube I6 beyond cut-oif whereupon the tube will clip variations caused in the signal by dial pulses or transmitter modulation.

The positive pulse 8V appearing in the plate output of tube IB is fed to the grid of cathode follower I9 and through the cathode thereof to conductor 2li which is multiplied to the grids of all line finder gate tubes 2|.

The line nder gate tubes 2l are normally biased through battery 22 far enough beyond cutoff so that the incoming positive pulse I8 will not aiiect their plate output.

A lock-in oscillator 23 in the line finder operates at a frequency slightly below the rate of scanning in the tubes 5 and 6 (200 kc), and divides this output to a frequency of approximately 50 kc. The sine wave output of oscillator 23 passes through a clipping amplifier and differentiating circuit 24 in the form of pulses 25 to a multi-vibrator 26 arranged to synchronize at approximately 10 kc. The output pulses 21 of a multi-vibrator 26 are differentiated in a network 23 and the resulting pulses 29 are applied to the control grid of a clipper gate tube 30. The constant and the bias of this gate tube are adjusted so as to produce by the leading edge of the differentiated pulses 29 in the plate circuit thereof a short square pulse 3| of approximately 5 microseconds duration. The trailing edge ofthe pulses 29 is suppressed in tube 30.

The negative pulse 3l is passed through a cathode follower 32 as pulse 33 which is applied to the cathode of the line finder gate 2l. Theaniplitude of pulse 33 is adjusted' by" delay gain-'tube 34 so that normally the line finder gate'tube'Zl-4 remains cut-off. This gate has apositive-'pulse I8 applied to its grid and a negative vpulse 33 to its cathode, neither of which will drive it beyond cut-oir to produce conduction. Since the lock-in oscillator 23 has a` Afrequency whichis slightly less than that of the master oscillator 1, the pulse 33 will drift with respect to the pulse I8 until` the two will occur simultaneously whereupon the bias of the lineinder 'gate tube is overcome. When this happens then'a negativesignal 34` appearing in the'plate is passed through a'rectiiier 35 and an integrating net`36 to the grids ofthe delayed gain tube 34 and of the gate control tube 31. vThe latter will Vbe driven to cut off after a few pulses 34 have reached it, permitting the lock-in gate tube 38 to pass a signal received from the' masteroscillator 1 over a wire 3S. `The output of the lock-ingate tube 38 willl synchronize Yoscillatorv 23 with oscillator 1. A phase corrector 4i! inserted betvveen'the plate of grid 3S and the oscillator' 2 3inseures` accurate adjustment. i

The portion of the rectied output of rectifier 35 which was fed tothe'grid of the delayed gain tube 34 will drive the latter beyond' cut-off lafter a'few pulses. The plate of tube 34-and the' screenH grid of clipper gate 39 are connected' to a cornmon-resistorV 4l. The screen'vcltag'e of gate'30` will, therefore, rise and willjcauyse an increase in the'amplitude of pulse 3l and, therefore, of pulse 33 lwhich is the pedestal pulse applied to the cathode of line finder gate 2l.' This will cause the grid of tube 2l to be' driven positive by the pulse H3 and clipping by grid `currentwill occur.

Howeverfthe amplitude "of' the incoming pulse' I3 will be insufhcientft'o affect the line finder gate 60 tube of any other link. The'output'pulses 34l of the line nder gate are applied also over conductor 42'to' the Ygrid of an'input gate control tube 43. rThe plateof tube 43 is connected in multiple to the'suppressor and output gate tubes 45 and 41 are normally biased to cut 01T on their suppressor grids by the voltage drop in plate resistor 49 Vof output gate control tube Ell;l i

The negative pulse 34 coming from the line finder gate drives the grid ofFcontrol tube 43V beyond cut-off which will reducethe voltage-drop across its plate resistor 48 to'zero.y This-willraise" the -bias on the suppressoi` grids of gates e4'4'alncl" 43,r permitting thepassage-of signals whichmay appear on the control grids of these gate tubes.`

Inizing p'ulsev Si flips conduction Vin 1 tl"1e,'No,.`A 0

It is assumed that speechand 4dial Yp11ls'eswil'l`u modulate the line signal-at, say,25%'.`- The c'lip' portion so that the pulse I8 which is applied to the line finder gate will be uniform. However,

a clipper tube 5l is so biased that only the modulated portion of a positive pulse 52 applied thereto by the inverter i4 will appear in the grid of a cathode follower 53. Cathode output '54 of tube 53 is applied over conductor 55 to the control grids ofthe input gate tubes 44r and 45 in all links but will affect only the pairl whose'control tube 43 is operated by the pulses 34.

The pulses produced by the dial 2 of the calling line will thus be transmitted as pulses 34 through gate control'43, and through the plate of input gate 44 over conductor 55 and a pulse stretcher and integrating network 51 to the grid I of an amplifier 58 'in the form of positive pulses 59, These lowv frequency dial pulses y59 are amplied by tube 548i and shaped in a clipper tube 33 toA form negative square Wave pulses 6l. The pulses 6i Iare differentiated in a network 62 into pulses 63 which are applied to the control grid of dial gate tube S4, The latter is biased sol that the lead-'ling edge of the differentiated pulse` 6 3,A isv suppressed and the trailing edge thereof is' passed as a negative pulse 65 over conductor, 66, to the" registerv circuits.

The pulses 59 are passed in parallel over apulse stretcher and integrating net H2, and the lead.- ing edge of the rst puls-e of a series flips con,- duction from tube S1` to tube 68 inthe dial .gate control. The circuitv constants are such as to, maintain this condition until the end of thexrdiall pulses when tube 61 again becomes conducting and sends arneg'ative'pulse'to the dialgatecon-- trol 69,Y 1U and to the., ringing gate controly |012, Ill3. The output o f tube 1ll` .isl applied over con-' ductor 1l to the suppressor 'grid of dial gate 64g biasing the latter to cut 0E. This willlockout the register so'as to protect it against transients.

The Vregister circuits are also conventionalI I Eccles-Jordan trigger circuits connected to form aY strip count. Initially, the right-hand tube 13 of the No. 0 register and the left-hand tube 14 invtheNo. 1 register and of all subsequent registers'vare conducting. Thev rst negative pulses, 65" on conductor 56 will transfer conduction in theV N o. 0 register from tube 13 to tube 12.. The negative pulse `appearing in the plate of tube 12 will. be applied to the `grid Vof' tube 14 in the No.Y 1 register so as to transfer conduction to tube 15,., of the latter. l The next pulse 65 will produce thesame op,-` erations as above explained, except that nov/', registers Nos. l (14A, 15) and 2 (15, '11)A will beinvolved.4 After a series of pulses 65, representing the dial pulses atvthe calling station,` have been receivedthe right-hand tube of ,one of the registers will' be in" conducting condition. Apo-y tential will be applied to `the suppressor grid .o'ffi the corresponding'time channel gate tube 18, 'i9'y or llnassociatedwith',this register, permitting the', passing ofja' 'sigr'ialI from thecontrol grid 'fofth'e' time channelgate.AH The line selecting circuit proceeds now to count the digit' pulses as set in the (register, synchrol nizing onyeach count with a `zero pulse 8l 'ape pliedto the'No. 0 counter over a `conductor82,r from a zero-pulse generator 83 Ywhich driyenk'j" by'thfe 1Q kc. frequencyydiyider il.;

Nermally, the'leftf-"hand .tubes 84,` 86,. 88 etc.V of the 'counters are conducting. The"s'ync`hr counter from 4.tube 184.1150: tube B5. Negativev pulses 92;' whichl are derived fromuma'ster"oscillator A'1 over conductors '39 and 93 and a pulselsh plied overa common conductor 95r to 'the grids of all the right-hand counter tubes 85, 81, 89 vand 9|.

The negative pulse 92 following the synchronizing pulse 8| will transfer conduction in the No. counter from tube 85 to tube 84.- vThe nega# tive pulse appearing in the plate circuit of 84 is applied to the grid of the left-hand tube 86 in the No. 1 counter and will flip conduction to 81.

Each successive pulse 92 will flip a counter so as to make its right-hand tube conducting until all the counters are operated, whereupon the final pulse restores the circuit to normal. Depending on the register which is operated, one of the time channel gate tubes 18, 19, etc. 80 will permit the passage of a signal which is applied to its control grid by the right-hand tube of the operated counter, and this pulse 95 is transmitted over conductor 91 to the control grid of the output gate control tube S. If, for example, the No. l register is conducting on its right-hand tube 15, then the positive bias on it is transferred to the suppressor grid of time channel gate tube 18, so that when the No. 1 counter flips conduction to its right-hand tube 81 a negative signal 96fwi1l be generated on the plate of tube 18.

The negative pulse 96 is applied over conductors 91 and 40, and a busy pulse-shaping amplifier |00 of the grid of a busy gatetube 0| Whose output added to the pulse I8 appearing in conductor 20 when the beam of 5 sweeps the called line will prevent the operation of a line finder gate tube like 2| when the called subscriber answers. Y Y

At the end of a series of dial pulses a negative pulse in the output of dial gate control tube B1 will ip conduction from a tube |02 to a tube |03 in the ringing gate control forming part of the ringing circuit. This will permit a ringing gate tube |04 to send a ringing signal over conductor |05 to the control grid of the output gate tube 41. Whenever the beam of the sending tube 5 sweeps over the dynode in which the called line terminates, ringing signal is applied through the following circuit: From a ringing oscillator |06 to the vsuppressor grid of ringing Vgate |04 which has been made operative by the potential applied to its control grid by the ringing gate control, the plate of tube |014, conductor |05, the control grid of output gate tube `41, the plate of tube 41, amplifier |01, the control grid of a pentode |08 whose supressor grid is controlled over conductor |09 by the dial gate control 69, 10, the plate of tube |08, conductor H0 and the control grid of the sending tube 6. The grid will so control the beam when it impinges on the dynodes of. the called line as to cause the operation of :a ringer at the called station. A

vWhen the beam of tube 5 next engages'the terminals of the called party who has answered, the `'positivepulse I0 on the cathode of triode |9 will be applied over conductor ||3 tothe con"- trol grid of trip ringing tube i4.' Thisjjtubelis now open by virtue of a positive pulse applied to its suppressor grid by triode ||5 which, in turn, is made at this instant coductive by pulse 96 applied to it by the corresponding time channel gate over conductor 91.

Negative pulses ||8 produced in the plate of ||4 will flip conduction from |03 to |02 in the ringing gate control whereupon ringing will stop.

The circuit is now ready to pass speech signals. Speech signals produced in the calling line will be sent when the dynode of this line is swept by the beam of receiver tube 5 over the anode I2, the cathode follower |4 to the clipper tube 5|, and thence to the cathode follower 53 and over conductor 55 to the control grid of the input gate tube 44. From the plate of input gate tube 44, the signal goes through a low pass filter ||1 where it is transformed from a series of pulses to the original speech frequency signal and applied to the control grid of the output gate 41. From the plate of the output gate the signal passes through the amplifier |01, the tube |08 and conductor 0 to the control grid of the sending distributor 6, and through the appropriate dynode thereof to the called line.

The path of the speech signals from the called line to the calling line will be the same as above described but it will occur when the receiving distributor 5 .sweeps over the dynode of the called line and the distributor 6 sweeps over the dynode of the calling line. Furthermore, the pulses 54 applied over conductor 55 will not affect the input gate 44 but the input gate 45 through whose plate it will be conveyed via another low pass filter ||8 to the control grid of the output gate tube 46, the output circuit of which is in multiple with the output circuit of the gate 41.

It will be seen, therefore, that the timing of. the two functions is reversed, the input gate control tube 43 operating input gate 44 and output gate 46, and the output gate control `tube 50 controlling the input gate tube `45 and the output gatetube 41.

At the termination of a call, when the calling subscriber hangs up, all circuits are released under the control of the delayed gain tube 34. The register circuit and the dial gates which are locked in are released by the release tube ||9, |20, and |2|. When the call is initiated the delay gain tube 34 is driven to cut-off, reducing the potential on the grid of tube |20 which is connected with the cathode of the delay gain tube 34 over conductor |22. This causes the obvious flip-flop circuit to transfer conduction to tube ||9 which sends a negative pulse through a differentiating network to the grid of tube |2|. The latter is biased beyond cut-off and the pulse has no effect. When, however, the line finder 2| releases, then ||9 again becomes conductive and applies a positive pulse to the grid of 2| A negative pulse |23 will then be applied .to the conductor |24 which will restore all the registers and the dial gate control tubes to normal.

What I claim is: 1. In a communication system, a plurality of` lines, two electronic means common to said lines,

each having a plurality of electrodes in which' the lines terminate and means for cyclically",

sweeping with an electron beam the electrodes, a control grid for the beam of the rst of `said means, a signal repeater having an output connected with said control grid, timing means for applying to the repeater signals originating on calling and called lines when the beam ofthe second of said electronic means sweeps over their terminals, a ringing circuit common to said lines,

line selecting means common to said lines, means"I area-ice trol grid for the beam, a source of signals common to said lines, said source comprising a ringing oscillator, a trigger circuit, means controlled by the timing means for operating said trigger circuit to connect the ringing oscillator with the repeater, and means controlled by the called line for operating said trigger circuit to disconnect the ringing oscillator, a signal repeaterl having an output connected with said control grid, timing means for applying to the repeater signals .originating on calling and called lines when the beam of' said electronic means sweeps over their terminals, and means controlled by said timing means for applying signals from said source to the repeater when the beam sweeps over the terminal of the called line.

3. In a communication system, a plurality of lines, electronic means common to said lines and having a plurality of electrodes in which the lines terminate and means for cyclically sweeping with an electron beam the electrodes, a control grid for the beam, a source of signals common to said lines, said source comprising ringing oscillator, .a ringing gate tube having a cathode, an anode, aV suppressor grid With which said oscillator is connected and a control grid, a connection from the anode tosaid repeater, a trigger circuit connected with said control grid, means controlled by the timing means for operating said trigger circuit, and means controlled by the called line for operating said trigger circuit, a signal repeater having an output connected with said control grid, timing means, for applying Ito the repeater signals originating on calling and called lines when the beam of said electronic means .sweeps over .their terminals, and means controlled by said timing means for applying signals from said source to the repeater when the beam sweeps vover .the terminal of the called line.

4. In a telephone system, .a plurality .or lines, two electronic means common to said lines, each having a plurality of electrodes in which the lines terminate and means for cyclically sweeping with an electron beam the electrodes, a control grid for the beam oi the first ci said means, a signal repeater ,having an output connected with said control grid, timing Imeans for applying .to the repeater signals Yoriginating on callingand called lines 'when the beam of the second ,of .said .electronic means sweeps `over their terminals, :a ringing oscillator, a ringing gate .tube having a cathode, an :.anode, a suppressor .'grid'with which said oscillator is connected and a control grid, `a connection from the anode to said repeater., a :trigger circuit connected with said `,control grids, means controlled .by the timing :means vfor oper. ating :said trigger` circuit, Aand Ameans controlled bythe called .line Vfor operating said trigger scircuit.

5. Ina telephone system, V-a plurality Aof lines, two cathode ray tubes common to ,said flines, each having a plurality of electrodes in which the 'lines terminate and means for cyclically sweeping with an electron beam the electrodes, a control gd for the beam of `the -rst tube, asignal lrepeater comprising two input and two output :gate tubes,A

each of said gate tubes having a cathode, an anode, a control and a suppressor grid, means including the second cathode ray tube for applying signals originating on the calling and called lines to the control grids of the input gates, connections including low pass lters from the anodes of the input gates tothe control gridsr of the output gates, a connection for applying a potential to the suppressor grids of one input and one out put gate controlled by the calling and called lines when their terminals are swept by the beam of the second cathode ray tube, a connection from the anodes of the output gates to the control grid of the rst cathode ray tube, a connection for ap-- plying a potential to the suppressor grids of the other input and output gates when the beam of the second cathode ray tube sweeps over the terminals of the called line, a ringing oscillation generator, and means for connecting said generator with the control grid of the other output gate when the beam of the rst cathode ray tube sweeps over the terminals of the called line.

A6. In a communication system, a plurality of lines, `electronic means common to said lines and having a plurality of electrodes in which rthe lines terminate and means for cyclically sweeping with an electron beam the electrodes, a control means for the beam, -a signal repeater having an output connected with said control means, timing means for applying to the repeater signals origi nating on calling and called lines, a ringing circuit common to said lines, line selecting means common to said lines, means associated with the calling line to operate the selecting means to se-J lect the called line, and means operative thereupon for operating said repeater bythe ringingI circuit.

7. In a communication system, a plurality oi lines, electronic switching means including a plurality of devices 'having `space discharge paths, means for establishing a connection between a calling and a called line solely through the space discharge paths of said devices in said electronic switching means, -a ringing circuit common to said lines, and electronic means comprising devices having discharge paths operative upon the establishment of said connection for 'connecting' the ringing ,circuit with the .electronic switching means to ring the called line. f

DAVID H. 'RANSOM.

REFERENCE S OITED 1The following references are of record in .the

le of this patent:

UNITED 4S'IA'ZUES PATENTS 

